There are a few factors when choosing a respirator.
The reusable, throw away types don't work. I have been in Construction my entire life, and they are great for a quick sweep of a jobsite floor but that's about it. They are of no use for filtering much fine dust particles, let alone, fumes.
If you are wanting a respirator to just filter fine dust particles, expect to pay at least $30. they sell refill cartridges for them, so you don't need to buy a new mask each time. The replacement cartridges may run $10 (for both), and will last hundreds of hours.
A mask that filters out fumes is another story, (Paint Thinner, Varnish, gasoline etc.) Expect to pay a bit more money for one. I'm not sure of the cost because I have never bought one. I would say it would be a bit overkill for the casual user.
You can get both that are respiratory only and with full face mask, Check out Home Depot, they have a fairly good variety, and well worth the purchase. For some like you JHP, I would say a full face apparatus would be good, since you have a business making powders.
It all really comes down to how much you want to spend. Spend at least $30 for a good one that will actually work.
Hope this helps.
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